This invention pertains to a fuel injection and ignition system for an internal combustion engine used for supplying fuel to and igniting the internal combustion engine.
Many vehicles such as a snowmobile, an outboard motor and a small two-wheeled vehicle have no battery mounted thereon. Of late, even an internal combustion engine driving such a vehicle having no battery mounted thereon has an electronically controlled fuel injection system (EFI) used as means to supply fuel and an ignition system including a microprocessor used to precisely control an ignition timing to ignite the engine for the purpose of purifying the exhaust gas and improving the startability of the engine.
In the fuel injection and ignition system for the internal combustion engine for driving the vehicle having no battery mounted thereon, there has been employed a power source system for applying a power source voltage to an injector, a fuel pump, an ignition circuit and a controller to control them from a magneto generator driven by the engine, which is referred to as xe2x80x9cMAG power systemxe2x80x9d hereinafter.
The internal combustion engine for driving such a small-sized vehicle using the MAG power source system is adapted to be generally started by a starter such as a rope starter or a kicking starter using human power.
Since the rotational speed of a crankshaft of the engine cannot get enough high when it starts using the human power starter such as the rope starter or the kicking starter, the generator driven by the engine cannot generate the high voltage. Thus, there are provided individual power source systems for applying the respective power source voltages to the injector, the fuel pump, the ignition circuit and the controller in order to start the engine by the limited electric power generated by the generator so that the output characteristics of the respective power source systems are made proper whereby the extremely low speed rotation when the engine starts causes no fault in which the injector cannot be driven due to shortage of the electric power for the controller and the fuel having the predetermined amount of injection cannot be injected due to the shortage of the fuel pressure caused by shortage of the driving electric power for the fuel pump even though the injector can be in the condition of being able to be driven and thus the startability of the engine is improved.
Such a prior art in which the electric powers from the individual power source systems are applied to the injector and the controller as aforementioned is disclosed in Japanese Utility Model No. 2573118 (JP2573118U). In this document, although power sources for the fuel pump and the ignition circuit are not described, the commercially available fuel injection and ignition system having the idea embodied has individual power source systems from which the power source voltages are applied to the fuel pump and the ignition circuit, respectively.
An example of the practically used power source system is shown in FIG. 7. A magneto generator 1 having a rotor mounted on a crankshaft of the internal combustion engine is provided on the side of a stator with a generation coil 1a for driving a fuel pump FP, a generation coil 1b for driving an injector INJ, a generation coil 1c for driving an ignition circuit, a generation coil 1d for driving a controller ECU and a generation coil 1e for driving a car body electric load 3 such as head lamps. These generation coils are wound on one pole (tooth) or a plural of poles of an armature core in accordance with the amount of electric power required for the load to which the electric power is supplied.
The outputs of the generation coils 1a through 1e are converted into DC voltages by respective power source circuits 2a through 2e including a voltage regulating rectifier circuit and a power source capacitor Cd connected across the output terminals thereof and supplied to the fuel pump FP, the injector INJ, the ignition circuit including an ignition coil IG, the controller ECU and the car body electric load 3, respectively. The controller ECU comprises a microprocessor MPU for arithmetically operating the ignition timing and the amount of fuel injection and, in addition thereto, comprises a switch Qf to control the energization of the fuel pump FP, a switch Qj to control the energization of the injector INJ and a switch Qi to the energization of a primary coil of the ignition coil IG. In the illustrated example, the ignition circuit is constituted by the ignition coil IG and the switch Qi.
Although, in the example shown in FIG. 7, the power source circuits 2a through 2e are provided separately from the controller ECU, in some case, the power source circuits 2a through 2e may be collectively formed with the controller ECU so as to form a single unit.
With the construction shown in FIG. 7, the controller can be operated at the extremely low speed of the engine by getting the proper output characteristic of each of the power source circuits 2a through 2e so as to perform the fuel injection and the ignition, which causes the startability of the engine to be improved.
However, in the construction of FIG. 7, there are required many generation coils having different characteristics in the single generator so that the power source circuit is provided for each of the generation coils. This causes the following problems;
(a) Since the winding operation should be made while copper wire is changed for every generation coil, the winding operation of the generator is troublesome, which causes the higher manufacture cost of the generator.
(b) Since many generation coils require the respective terminal treatment, this needs a number of steps for the terminal treatment, which also causes the higher manufacture cost of the generator.
(c) Since the number of the wires of the wire harness led out from the generator increases, the laying operation of the wire harness gets troublesome.
(d) Since the number of the power source circuits increases, the cost of the power source section gets higher.
The vehicles such as the snowmobiles or ATVs (buggies) considered to be used in the out-of-the-way places or the vehicles such as the motorboats having a possible accident, which would occur if the engine stops, are preferably in the condition where the internal combustion engine can be operated even in the case where the batteries cannot be used.
The MAG power source system is the one excellently used for the case where the engine is laid under such a circumstance of extremely low temperature as cannot guarantee an output of a battery enough to enable the fuel injection system and the ignition system to be driven without relying on the battery after the engine starts and before it is steadily operated or the case where the engine is required to be operated even though the battery is deteriorated.
However, since the prior MAG power source system has a number of power source circuits as shown in FIG. 7, the system could be inevitably more expensive than the ordinary power source system having the battery used.
In Japanese Patent Application Laid-Open Publication No. 2002-21624 (JP2002-21624A), it is disclosed a start control system in which a power source section is so constructed that the fuel pump, the injector and the ignition system can be driven by a single power source circuit having a generator used as a power source and in which, when the engine starts, the fuel pump, the injector and the ignition system never serve simultaneously as the load to the power source circuit by stopping the operation of the fuel pump when the injector and the ignition system are driven in the course of starting the engine.
According to the start control system disclosed in JP2002-21624A, since the number of the power source circuits provided in the power source section can be decreased, the cost of the system can be reduced.
However, in this system, since the operation of the fuel pump stops when the fuel should be injected in the course of starting the engine, and the fuel is injected by the fuel pressure previously accumulated in a fuel pipe system before the injection of the fuel, the amount of fuel injection will be less than the desired amount of fuel injection according to the accumulated fuel pressure. This causes the ratio of air to fuel of the mixture gas to get leaner and therefore the startability of the engine to be possibly deteriorated.
In the case where the fuel pump is adapted to stop when the fuel injection and the ignition operation are performed at the time of starting the engine, the fuel pump is intermittently driven in the course of starting the engine. Thus, when the engine is started after the engine stops for long time, it will take substantial time for the fuel pressure applied to the fuel injector to increase to the normal value whereby the startability of the engine is possibly deteriorated because of the insufficient amount of fuel injection when the engine should be started.
Accordingly, it is a principal object of the invention to provide a fuel injection and ignition system for an internal combustion engine in which the number of power source circuits provided in a power source section can be decreased so as to reduce the cost of the system and the startability of the engine can be improved without any possible insufficient of amount of fuel injection when the engine should be started.
This invention pertains to a fuel injection and ignition system for an internal combustion engine comprising an injector to supply fuel to the internal combustion engine, an ignition circuit to generate an ignition high voltage to be applied across an ignition plug provided in a cylinder of the internal combustion engine, a controller to control at least the injector and the ignition circuit and a power source section having an AC generator as a power source to apply a power source voltage to the injector, the fuel pump, the ignition circuit and the controller.
In the invention, the power source section is adapted to apply the power source voltage from a single voltage regulating power source circuit through a power source line to the controller and the fuel pump and at least one of the injector and the ignition circuit.
The controller comprises pump drive current control means to control a drive current for the fuel pump in a PWM mode so as to maintain the power source line voltage at a reference voltage or more, which is determined at a voltage or more corresponding to the minimum operation voltage of the elements other than the fuel pump, in the course of starting the engine.
With the common single power source circuit provided for the controller and the fuel pump and at least one of the injector and the ignition circuit, the number of the power source circuits provided in the power source section can be reduced and therefore the cost of the system can be decreased. Also, the number of the generation coils provided in different systems of the generator can be reduced, the number of winding operation of the generator can be decreased, which reduces the number of the harness led out of the generator whereby the generator can be inexpensive.
Furthermore, with the aforementioned construction, since the operation of the fuel pump can be continued even when the fuel injection and the ignition operation are performed in the course of starting the engine, there can be prevented the possible insufficient fuel pressure, which tends to occur in the prior art in which the fuel pump stops when the fuel injection and the ignition operation are performed in the course of starting the engine. Therefore, there can be prevented the state where the amount of fuel injection becomes insufficient when the engine should be started, which can always accomplish the improved startability of the engine.
In a preferred embodiment of the invention, the power source section is adapted to apply the power source voltage from a single voltage regulating power source circuit having a generator as a power source through the power source line to the injector, the ignition circuit, the controller and the fuel pump.
In this case, the pump drive current control means of the controller controls the drive current for the fuel pump in the PWM mode so as to maintain the power source line voltage at the reference voltage or more, which is determined at the voltage or more corresponding to the higher minimum operation voltage among those of the injector and the ignition circuit.
According to the invention, since the power source voltage from the single power source circuit can be applied to the injector, the ignition circuit, the controller and the fuel pump, which are the fundamental elements essential for the operation of the internal combustion engine, the power source section can be constructed in a simpler manner than the one in which the electric power is applied to one of the injector and the ignition circuit through the other element.
In the invention, in the case where the power source voltage is applied from the same power source circuit as the one which applies the power source voltage to the fuel pump and the controller to only one of the injector and the ignition circuit, the power source voltage is adapted to be applied to the other element of the injector and the ignition circuit through a circuit of system different from the system of the power source circuit. With the system constructed as aforementioned, the construction of the power source section can be more remarkably simplified than the prior fuel injection and ignition system in which there are provided the individual power source systems for the injector, the fuel pump, the ignition circuit and the controller, respectively.
In a further preferred embodiment of the invention, a load or loads such as a lump load other than the injector, the ignition circuit, the controller and the fuel pump is connected through energization control switch means to the power source line. In this case, the controller may further comprise, in addition to the aforementioned pump drive current control means, energization control switch means to control an energization control switch in a PWM mode so as to provide an off state of the energization control switch when the engine should be started and to maintain the power source line voltage at an objective voltage set at the reference voltage or more after finishing the start of the engine.
The power source circuit comprises a control rectifier circuit of a hybrid bridge circuit of diodes and thyristors, from which the power source voltage is output to the power source line. In this case, in the power source section or the controller, it may be provided thyristor control means to control the thyristors so as to limit the power source line voltage to a predetermined limited value or less.
In the case where the generator comprises a magneto generator, a voltage regulation to lower the output voltage of the generator to the limited value or less can be performed by shorting the output of the generator when the output voltage of the generator gets excessive. Thus, in this case, the power source circuit may comprise a rectifier circuit to rectify the output voltage of the generator and an output shorting switch to short the output of the generator so as to output the power source voltage from the rectifier circuit to the power source line.
In this case, in the power source section or the controller, it is provided output shorting switch control means to control the output shorting switch so as to short the output of the generator when the power source line voltage exceeds the predetermined limited value.
The aforementioned power source circuit may comprise a rectifier to rectify an output current of the generator and a chopper switch to intermittently flow the output current of the generator whereby the voltage rectified by the rectifier and regulated by the chopper switch is output to the power source line.
In this case, in the power source section or the controller, it is provided chopper control means to control the chopper switch so as to rise the power source line voltage when the voltage of the power source line is lower than the predetermined limited value due to the lower rotational speed of the internal combustion engine and to lower the power source line voltage when the power source line voltage is higher than the limited value.
With the system constructed as aforementioned, since there can be fed the DC voltage higher than a crest value of the output voltage of the generator to the power source line by rising the output voltage of the generator, the starting rotational speed of the engine or (the rotational speed when the fuel injection and the ignition start) can be lowered whereby the startability of the engine can be improved.